I tried it using MCWS, it has the same problem I mentioned earlier regarding not updating the current zone. It means
start playback in 1 zone and be watching the display
send the divert command
view switches to the playing now view
original zone is still current so if you press ctrl+3 then it shows a black screen because nothing is playing there
IME controlling display view programmatically is really slow (and quite flaky) but I guess it could automated (divert, setactivezone, change display mode) via some script
I'd say technically possible but really clunky and a bit slow
thanks for the tip though, it's not far away from being usable